This project, in collaboration with Drs. John Carpten and Jeffrey Trent of NHGRI and with Drs. Maurine Hobbs, Raj Thakker, Bin Teh, Catharina Larrson, R. Marks and Silvano Presciuttini, aimed to narrow the region on chromosome 1 where a locus for hyperparathyroidism with jaw tumors (HPT-JT) had been mapped by several previous linkage studies, and to eventually clone and characterize this gene. The gene has been localized and characterized within the region indicated by our fine-mapping analyses. A manuscript was published in this fiscal year in Nature Genetics that presented the linkage, and cloning results. In the future, we plan to use these data to examine questions about our haplotype sharing method and its uses in localizing disease genes. We are also planning future studies of the penetrance of various mutations at this locus and of possible gene-environment interactions between susceptibility alleles at this locus and various environmental risk factors.